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A Watch-Movement Primer

By

Paul Boutros

July 4, 2014 3:14 a.m. ET

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By

Paul Boutros

July 4, 2014 3:14 a.m. ET

Watch-collecting novices generally know that the industry is divided between high-end mechanical watches, powered by a mainspring, and mass-market quartz watches, powered by a battery. After that, things get fuzzy. Mechanical-watch movements are built out of springs that provide power (mainspring) and regulate power (hairspring); gears and levers, which transmit the power of the mainspring; and finally bridges, which are the structural elements that hold all movement parts in place. For a detailed explanation, pick up Donald De Carle's Watch & Clock Encyclopedia and George Daniels' detailed Watchmaking. To see exposed movements in all their glory, track down Guido Mocafico's magnificent photography book Movement.

But let me help with the learning curve, too. Mechanical watches are either manual or automatic. A movement's long, coiled mainspring is "energized" when wound; in a manual watch that's done by turning the round winding crown on the side of a watch until the mainspring is loaded with energy. In automatic watches, a heavily weighted rotor inside the case, sometimes made of gold or platinum and constantly spinning with the wearer's wrist movements, winds up the mainspring. As the mainspring releases its tension, gears are powered into motion; the rate at which the mainspring unwinds is regulated by the oscillation of a balance wheel and balance spring, also known as the escapement. The escapement maintains timekeeping accuracy, converting the mainspring's energy into precisely measured beats. Beating at a rate of three to six times per second, the escapement's oscillation produces that wonderful ticktock—a sound like a heartbeat, the reason that collectors claim mechanical watches, not quartz, have a soul.

Breguet's Tourbillon Quantième Perpétuel is designed to show the watch wearer its glorious inner workings.
Photo: Paul Boutros/Time Zone

Consider the second hand. It's driven by the escapement's oscillation rate, providing a constant, sweeping motion of seconds through its quick steps around the dial. But the higher the oscillation rate of a regulator, the greater the accuracy, which is why quartz watches, with their typical 32,000 oscillations per second, are more accurate than mechanical watches. Still, a top-grade mechanical watch that's well maintained will only lose two to four seconds a day. With 86,400 seconds in a day, we're talking 99.99% accuracy.

ANY FUNCTION BEYOND HOURS and minutes is known as a "complication," and adds complexity, cost, and desirability. A basic movement might have 150 parts; a highly complicated movement, in the region of 1,000 parts. The power reserve, which measures and displays the remaining hours of power in the mainspring, is a complication. But so are date and calendar functions that can depict phases of the moon or show the day, date, and month within three subsidiary dials. The chronograph is a stopwatch complication used to measure elapsed time between the start of an event and its completion.

In high-end watches, the four most complex complications are known as grand complications and are highly sought after by collectors. The perpetual calendar mechanically accounts for months with 30 days, 31 days, the month of February, and leap years. So long as the watch remains wound, the calendar rarely needs adjustment. Perpetual-calendar wristwatches begin at approximately $13,000 at retail. The split-seconds chronograph, meanwhile, is a complex variant of a chronograph, enabling, for example, the timing of an individual's specific laps while simultaneously keeping track of the time for an entire race. Split-seconds chronographs begin at about $10,000.

Gravity can negatively affect a watch's escapement, so the greatest watchmaker, Abraham-Louis Breguet, in 1801 devised a mechanism called a tourbillon to counter its effects. The escapement is built inside a rotating cage; it's designed to complete one full revolution typically every 60 seconds, thereby averaging out and cancelling gravity's effects. It's debatable whether a tourbillon really improves a watch's accuracy, but they are beautiful, and today the tourbillons' whimsical rotations are often showcased through a dial window. At a price. Tourbillon wristwatches begin at $40,000.

In the days before electricity and glow-in-the-dark materials like radium, wealthy insomniacs wanted to tell the time in the dark. Watchmakers developed the minute repeater, a complex system where at least two gongs are struck by tiny hammers, like a mini-grandfather clock. The mechanism uses a delightful sequence of tones to chime the time down to the nearest minute. Minute-repeating wristwatches begin at $150,000.

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